One of the coolest things one could install on a positive pressure car is an Air Fuel (aka AF) gauge. These aren't scientific in any way and are minimally useful without other more sophisticated tools. One critical consideration is how to calibrate an AF gauge for accuracy? I won't get into the science behind. From Wikipedia
"Air-fuel ratio (AFR) is the mass ratio of air to fuel present during combustion. When all the fuel is combined with all the free oxygen, typically within a vehicle's combustion chamber, the mixture is chemically balanced and this AFR is called the stoichiometric mixture. AFR is an important measure for anti-pollution and performance tuning reasons...."
This is essential for a force-fed automobile like the Corrado. If the fuel mixture is too rich with fuel, performance suffers and damage to critical components such as the catalytic converter can occur. In severe cases, the excess fuel will dilute oil lubrication in the cyclinders.
Even more severe, if the fuel becomes too lean (too much oxygen) the engine could detonate. For the most part, the AF ratio should remain near 14:1.
In the corrado, the AF guage will indicate(guesstimate) the air fuel ratio based on oxygen content of the burnt fuel exiting the exhaust manifold. This is measured by the O2 sensor in front of the catalytic converter.
The corrado is already equipped with an O2 sensor which feeds much of this data to the Electronic Control Unit. Most will tap into this signal to feed the impulses to the AF gauge.
This is another issue where I diverge from conventional practice. I won't touch the O2 sensor wiring. These impulses are measured in millivolts. Interruptions or corruptions in this dataflow to the ECU can cause operational problems. In addition, those wires are constantly exposed to the extreme temperatures of the exhaust system increasing resistance in the wiring. After several years, these wires become brittle and fragile. Another reason to leave it alone.
I opted to have a small heat shield removed from the downpipe. This exposes a section of the downpipe upstream of the catalytic converter. For a few dollars, a competent muffler technician can install a threaded bung and you can install a dedicated O2 sensor to feed the AF gauge.
I purchased a simple single wire O2 sensor from my local autoparts store for roughly $30. Screwed it into the bung and we are ready to go.
Wiring was as simple as running a wire to the location for the gauge. I opted to get the gauge pods for the A-pillar which I purchased from New Dimensions. It holds two 2 1/16" gauges. Auto Meter makes an AF gauge which is very similar to the VDO Vision series. I believe VDO makes the gauges for VW but the vision series is identical to OEM gauges. I purchased the gauge from egauges. com. They have a full line of dashboard gauges and when I discussed my intentions, their knowledgeable staff made excellent recommendations.
The wiring was easy and I wrapped the single wire with hightemp silicone wrap. The O2 sensor takes some time to warm up but once it reaches operating temperature, the AF gauge lights up. It is active and responds instantaneously to engine loads. Very unique and a cool addition to a corrado dashboard.
Above, the dedicated O2 sensor as seen from below
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